Hydrocarbon conversion process



Fled Sept. l0, 1962 @en x x6. n@ MQ.

United States Patent O 3,240,831 HYDROCAREON CONVERSON FROCESS Gregory ll. Cottington, Groves, Tex., assigner to yexaco inc., New Yerk, N517., a corporation oi' Texas Filed Sept. 10, 1962, Ser. No. 222,339 9 Claims. (Cl. Zeil- 672) This invention relates to a hydrocarbon conversion process and more particularly to the production of hydrocarbon fractions rich in aromatics. In accordance with the process of this invention, a hydrocarbon oil having an initial true boiling point above 520 F. and preferably above 600 F. is subjected to catalytic cracking and an aromatic fraction boiling wholly below the initial boiling point of said feed oil is separated by distillation. In one embodiment of the process of this invention, a hydrocarbon oil having an 4initial true boiling point of at least 520 F. is contacted with a cracking catalyst effecting conversion of at least a portion of said hydrocarbon oil to lower boiling cracked products, said cracked products are fractionally distilled separating an aromatic fraction boiling Within the range of 430 to 520 F., and said aromatic fraction is subjected to hydrodealkylation producing naphthalene.

Heretofore, the products of catalytic cracking have been considered as possible sources or intermediates for the production of aromatics. However, the aromatics in the cracked products of typical cracking operations are diluted with non-aromatics of the same boiling range and separation of the aromatic constituents requires expensive concentration methods. Catalytic cracked oils boiling Within the range of 430 to 520 F. from full range feed stocks typically may contain within the range of about 30 to 60 percent aromatics about to 20 percent paraiiins, about 10 to 60 percent naphthenes and about 0 to 10 percent olens. Since the different hydrocarbon constitutes all boil within the same range, `separation requires means other than simple distillation, for example, solvent extraction, selective adsorption, azeotropic distillation, or extractive distillation. In accordance with this invent-ion a product unexpectedly high in aromatics boiling within 3,240,831 Patented Mar. 15, 1966 ICC the range of about 400 to 650 F. is produced by catalytic cracking of an oil feed boiling wholly above the boiling range of the desired aromatic product. The 430-520 F. cracked product produced by catalytic cracking o-ils boiling wholly above 520 F. typically contains above 70 percent aromatic hydrocarbons with the balance principally parafnic hydrocarbons.

`Cracking may be effected in uidized beds, fixed beds or moving beds of natural or synthetic csacking catalysts foh example natural clays or synthetic silica-alumina or silica-magnesia catalysts. Cracking conditions include, for example, temperature Within the range of about 825 to 1050" F., conversion levels expressed as yield of material boiling below 430 F. of within the range of about to 95 volume percent, catalyst to oil ratios of about 5 to 30 and weight hourly space velocities within the range of about 0.5 to 2.0. An advantage of the method of this invention is that the products of cracking boiling in the range of 430 to 520 F. are highly aromatic so that a portion of this range containing at least percent aromatics and readily containing percent aromatics may be separated from the cracked products by distillation alone. If an aromatic fraction of higher purity than that separated by distillation is desired, additional purification may be effected by solvent refining, extractive distillation or azeotropic distillation of t-he 430 to 520 F. aromatic fractions.

Feed stocks for the cracking step of the process of this invention comprise hydrocarbon oils having initial boiling points above about 520 F. and preferably above about 600 F. by true boiling point distillation. True boiling point distillation as used herein refers to a distillation with at least 30 theoretical plates and at least 5 to 1 reflux ratio. Initial true boiling point is the temperature in such a distillation when the rst liquid distillate is collefted. Although high yields of aromatic oils may be produced from such highly parainic feeds as paraffin wax, gas oils and extracts of a naphthenic or aromatic nature are preferred. The results obtained in cracking a number of hydrocarbon oils with a silica-alumina cracking catalyst are vshown in Table I.

Table l A B C D E Extract from Mixture of Virgln Gas Dewaxed Furural Virgin Gas Virgin Gas Oil Oil Virgin Gas Benning Virgin Oil and Deasphalt- Oil Gas Oil ed Residuum Charge Stock:

Refractive Index at 70 C 1. 4720 1. 4784 1. 5293 1. 4854 1.4782 Gravity, API 28. 8 26. 9 15. 7 24. 3 28. 7 Flash, COC, F 410 410 400 445 410 Viscosity:

SUS/100 F 142. 7 169. 2 491. 2 431. 0 290 SUS/210 F 42. 5 43. 6 51. 8 56. 0 50. 7 Distillation, F.:

IBP 646 622 628 630 615 50 779 753 760 825 774 90 825 801 811 893 941 807 826 914 Cracking Conditions and Yiel Temperature, 1, 000 1, 000 1, 000 1, 000 900 Space Velocity, v./l1r./v 1. 5 1. 29 1. 38 1. 34 1. 25 Catalyst to Oil Ratio 7.0 7. 36 6.86 7. 11 7. 57 Conversion, Vol. percent below 430 F 55. 1 67. 5 61. 4 71. 4 61. 6 Yield of 430 F. IBP Aromatic Oil 10. 9 12. 7 16. 4 14. 3 13. 4 430 IBP Aromatic Oil Quality' RI at 70 C 1. 5156 1. 5170 1. 5508 1. 5284 1. 5122 Gravity, 21. 7 20.9 13.1 18. 2 22.8 Flash, F 240 255 265 255 265 Kinematic Viscosity:

CS. at F 3. 04 2. 84 3. 00 3. 29 2. 98 CS. at 210 F 1. 16 1.12 1. 15 1. 19 1.16 Aromatics, Vol. percent- 83. 7 84.2 95. 2 86. 2 84. 9 Distillation:

IBP 430 430 430 430 430 End Point 646 622 628 630 615 The accompanying drawing diagrammatically illustrates one form of the process of this invention. Although the drawing illustrates one arrangement of apparatus in which the process of this invention may be practiced, it is not intended to limit the invention to the particular apparatus or materials described.

In the figure, a full range catalytic cracking feed stock having an initial boiling point of 430 F., a 50% point of 645 F. and a 90% point above 760 F. is passed through line to distillation tower 11. A light gas oil boiling in the range of about 430 to 600 F. is distilled overhead from tower 11 and discharged through line 13. This light gas oil may be separately cracked or may be employed for distillate fuel blending, not shown. Bottoms withdrawn from distillation tower 11 in a yield of 66% have an initial boiling point of 600 F., a 50% point of 685 F., and a 90% point above 760 F. This 600 IBP cracking stock is passed through line 14 to catalytic cracking facility 15. Cracking is effected at a temperature of 912 with a silica alumina catalyst, a catalyst to oil ratio of 11.0, and a Weight hourly space velocity (w./hr./w.) of 0.78. A conversion, expressed as volume percent of products boiling below 430 F., of 63.8% is obtained. Cracked gas is discharged through line 17, gasoline through line 18 and cracking residue through line 19.

Products boiling above 400 F. are passed through line to distillation tower 26. An aromatic oil boiling within the range of 400 to 430"k F. is distilled overhead and discharged through line 27. Tower bottoms are withdrawn through line and passed to distillation tower 31. In tower 31 an aromatic fraction having a boiling range of 430 to 520 F. is distilled overhead and bottoms boiling above 520 F. are discharged through line 33 and recycled to the catalytic cracking feed in line 14.

The 430 to 520 F. aromatic fraction contains 93% aromatics of which about 60% are alkylnaphthalenes. The 430 to 520 F. aromatic fraction is passed through line 32 to hydrodealkylation facility 35. Hydrodealkylation is effected at a temperature within the range of 900 to 1400 F., a pressure of 0 to 1000 p.s.i.g. with a hydrogen to hydrocarbon mole ratio within the range of 3 to 25, and with or without a catalyst. Advantageously hydrodealkylation facility 35 may include hydrogen treating facilities for the reduction of sulfur. Hydrodealkylation effects removal of alkyl side chains from alkylnaphthalenes and may be accompanied by the formation of naphthalene by other reactions, for example dehydrocyclization. Gas is discharged through line 36, polymer through line 37, and naphthalene product is discharged through line 38.

The 400 to 430 F. aromatic oil discharged through line 27 comprises naphthalene in admixture with nonnaphthalene hydrocarbons of the same boiling range. This stream may be separately treated to recover naphthalene by a severe cracking treatment, not shown. Since naphthalene is highly refractory, severe cracking effects conversion of non-naphthalene constituents to lower and higher boiling products without substantially effecting the naphthalene and pure naphthalene may be separated from the products of severe cracking by distillation.

A 28 API gas oil cracking stock having an IBP of 585 F. and a 5 percent point of 702 F. is charged to a uid catalyst cracking unit at a rate of 33,260 barrels per day where it is cracked in contact with a silica-alumina cracking catalyst. Products of cracking are separated into gas, gasoline, gas oil and cracked residue fractions. The gas oil fraction is further distilled separating an aromatic fraction boiling within the range of 430 to 520 F. The aromatic fraction is produced at a rate of 1996 barrels per day and contains 76.1 volume percent aromatics. In comparison, when catalytic cracking a full boiling range cracking stock having an initial boiling point of about 430 F. at the same conversion level, the gas oil product boiling within the range of 430 to 520 F. contains about 45 to 50 volume percent aromatics. A gas Oil fraction of such aromatic concentration is unsuited as feed for hydrodealkylation since the non-aromatic constituents consume an unordinarily large amount of hydrogen and the resulting product contains so much nonaromatic material coboiling with naphthalene that the separation of high. purity naphthalene by distillation is not feasible.

The 430 to 520 aromatic fraction is treated with hydrogen, at a rate of 3,000 standard cubic feet per barrel in the presence of a cobalt molybdate catalyst at a temperature of 805 F., and a pressure of 500 pounds per square inch gauge, effecting consumption of hydrogen at a rate of 276 standard cubic feet per barrel and reduction of the sulfur from 0.56 weight percent to less than 0.01 weight percent. The desulfurized aromatic fraction is thermally dealkylated at a temperature of l400 F. in the presence of hydrogen. The hydrodealkylated product is distilled producing 265,000 pounds per day of naphthalene of 99.8 percent purity.

I claim:

1. The method of producing an aromatic oil which comprises contacting a virgin gas oil fraction feed stock having an initial boiling point of at least 520 F. with a silica alumina cracking catalyst under conditions effecting conversion of at least 45 percent of said virgin gas, oil fraction feed stock to products boiling below 430 F. and distillatively separating an aromatic product fraction boiling within the range of about 430 to 520 F. containing at least 70 percent aromatics.

2. The method of producing naphthalene which cornprises contacting a virgin gas oil fraction feed stock having an initial boiling point of at least 520 F. with a silica alumina cracking catalyst under conditions effecting conversion of at least 45 percent of said virgin gas oil fraction feed stock to products boiling below 430 F., distillatively separating an aromatic product fraction boiling within the range of 430 to 520 F. containing at least 70 percent aromatics, hydrodealkylating said fraction boiling within the range of 430 to 520 F., and separating naphthalene.

3. The process of claim 2 wherein said virgin gas oil fraction feed stock has an initial boiling point of at least 600 F.

4. The method of producing an aromatic oil which comprises contacting a virgin gas oil fraction feed stock having an initial boiling point of at least 520 F. with a silica alumina -cracking catalyst at a temperature within the range of about 825 to 1,050 F., at a catalyst to oil ratio of within the range of about 5 to 30, a weight hourly space velocity within the range of about 0.5 to 2.0, and at a conversion to products boiling below 430 F. of at least 45 volume percent, and distillatively separating a product fraction boiling within the range of 430 to 520 F. containing at least 70 volume percent aromatics.

5. The process of claim 4 wherein said aromatic fraction is hydrodealkylated producing naphthalene.

6. A method of producing naphthalene which comprises distilling a hydrocarbon oil separating a virgin gas oil feed stock having an initial boiling point of at least 600 F., contactng said virgin gas oil feed stock with a silica alumina cracking catalyst at cracking conditions effecting conversion of at least 45 percent of said hydrocarbon oil to products boiling below 430 F. distillatively separating a rst fraction boiling within the range of 400 to 430 F. and a second fraction containing at least 70 percent aromatics boiling within the range of 430 to 520 F. from said cracked products, subjecting said first fraction to cracking conditions effecting conversion of nonnaphthalene constituents to higher and lower boiling materials, distillatively separating naphthalene from said higher and lower boiling materials, subjecting said second fraction to hydrodealkylation forming hydrodealkylation product comprising naphthalene, and distillatively separating naphthalene .from said hydrodealkylation product.

7. A method of producing naphthalene which comprises catalytically cracking a virgin gas oil fraction boiling above 600 F. with a silica alumina cracking catalyst at a catalyst to oil ratio within the range of 5 to 30, a weight hourly space velocity within the range of 0.5 to 2.0, a temperature within the range of 825 to 1,050 F. eifecting conversion to cracked products boiling below 430 F. of at least 45 Volume percent, distillatively separating a fraction boiling within the range of 430 to 520 F. containing at least 70 percent by volume aromatics, hydrotreating said 430 to 520 F. fraction forming a hydrotreated fraction, hydrodealkylating said hydrotreated fraction forming hydrodealkylation product comprising naphthalene, and distillatively separating naphthalene from said hydrodealkylation product.

8. The method of producing an aromatic oil whichv comprises contacting a virgin gas oil fraction feed stock having an initial boiling point of at least 520 F. with a silica alumina cracking catalyst under conditions effecting conversion of at least 45 percent of said virgin gas oil fraction feed stock to products boiling below 430 F. and distillatively separating a product fraction containing at least 70 percent aromatics 'boiling within the range of about 430 F. to said initial boiling point of said virgin gas oil fraction feed stock.

9. The method of producing an aromatic oil which comprises contacting a Virgin gas oil fraction feed stock having an initial boiling point of at least 520 F. with a silica alumina cracking catalyst at a temperature within the range of about 825 to 1050 F., at a catalyst to oil ratio within the range of about 5 to 30, at a weight hourly space Velocity within the range of about 0.5 to 2.0 and at a conversion to products boiling below 430 F. of at least volume percent, and distillatively separating a product fraction containing at least percent aromatics boiling within the range of 430 F. to said initial boiling point of said Virgin gas oil fraction feed stock.

References Cited by the Examiner UNITED STATES PATENTS 2,698,869 1/1955 Hetzel 260672 2,766,306 10/1956 Heinemann et al. 260-672 2,772,214 11/ 1956 Langer 208-67 2,880,251 3/1959 Jezl et al. 260-672 3,008,895 11/ 1961 Hansford et al. 208-68 3,050,457 8/ 1962 Wilson 208-67 3,145,238 8/ 1964 Kestner 260-672 3,150,196 9/1964 Mason 260-672 PAUL M. COUGHLAN, Primary Examiner.

JOSEPH R. LIBERMAN, ALPHONSO D. SULLIVAN,

Examiners. 

1. THE METHOD OF PRODUCING AN AROMATIC OIL WHICH COMPRISES CONTACTING A VIRGIN GAS OIL FRACTION FEED STOCK HAVING AN INITIAL BOILING POINT OF AT LEAST 520*F. WITH A SILICA ALUMINA CRACKING CATALYST UNDER CONDITIONS EFFECTING CONVERSION OF AT LEAST 45 PERCENT OF SAID VIRGIN GAS, OIL FRACTION FEED STOCK TO PRODUCTS BOILING BELOW 430*F. AND DISTILLATIVELY SEPARATING AN AROMATIC PRODUCT FRACTION BOILING WITHIN THE RANGE OF ABOUT 430 TO 520*F. CONTAINING AT LEAST 70 PERCENT AROMATICS. 